There are known electric tools in which a brushless direct current motor (DC motor) is employed and a controller such as a microcomputer performs control over the rotation of a motor with high accuracy. The brushless DC motor detects a rotation position of a rotor using a magnetic sensor, and the controller controls a drive current supplied to a winding coil of the motor. Patent Document 1 discloses a technology as an example of an electric tool (grinder) employing a brushless DC motor. In Patent Document 1, the brushless motor is accommodated in a manner of being coaxial with a cylindrical housing. In the motor, a stator having a coil is disposed on an outer circumferential side, and a rotor core which rotates by means of a rotary shaft and holds a permanent magnet is provided on an inner circumferential side. The rotary shaft is pivotally supported by bearings on the front side and the rear side of the motor. A cylindrical sensor magnet for detecting the rotation position of the rotor is provided behind the rear bearing. The controller and a power supply circuit for controlling the motor are accommodated inside the housing on the rear side. In addition, an inverter circuit for supplying a rotating magnetic field (three-phase alternating current) to the coil of the motor is loaded. In an electric tool in which a brushless motor is loaded, switching elements such as field effect transistors (FETs) are required in order to drive the motor. Since the switching elements generate heat, the switching elements are required to be cooled using a cooling fan or the like. In the technology of Patent Document 1, the power supply circuit and the inverter circuit are loaded in circuit substrates independent from each other. In addition, the switching elements are loaded in the inverter circuit, and the switching elements are loaded at positions exposed to an air passage of cooling air generated by the fan.